Implantable medical device with recharge coil

ABSTRACT

Implantable medical device (IMD) such as leadless cardiac pacemakers may include a rechargeable power source. In some cases, the IMD may include a plurality of receiving coils that may capture a non-radiative near-field energy and then convert the near-field energy into electrical energy that may be used to recharge the rechargeable power source. Accordingly, since the rechargeable power source does not have to maintain sufficient energy stores in a single charge for the entire expected life of the IMD, the power source itself and thus the IMD, may be made smaller while still meeting device longevity expectations.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/424,930 filed on Nov. 21, 2016, the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The disclosure relates generally to implantable medical devices, and more particularly to implantable medical devices that have a power source that may be wirelessly recharged from a remote location.

BACKGROUND

Implantable medical devices are commonly used to perform a variety of functions, such as to monitor one or more conditions and/or delivery therapy to a patient. In some cases, an implantable medical device may deliver neurostimulation therapy to a patient. In some cases, an implantable medical device may simply monitor one or more conditions, such as pressure, acceleration, cardiac events, and may communicate the detected conditions or events to another device, such as another implantable medical device or an external programmer.

In some cases, an implantable medical device may be configured to deliver pacing and/or defibrillation therapy to a patient. Such implantable medical devices may treat patients suffering from various heart conditions that may result in a reduced ability of the heart to deliver sufficient amounts of blood to a patient's body. In some cases, heart conditions may lead to rapid, irregular, and/or inefficient heart contractions. To help alleviate some of these conditions, various devices (e.g., pacemakers, defibrillators, etc.) may be implanted into a patient's body. When so provided, such devices can monitor and provide therapy, such as electrical stimulation therapy, to the patient's heart to help the heart operate in a more normal, efficient and/or safe manner. In some cases, a patient may have multiple implanted devices that cooperate to monitor and/or provide therapy to the patient's heart.

In some cases, implantable medical devices must be relatively small. For example, leadless cardiac pacemakers are typically relatively small because they are often placed within the heart. Due to their relatively small size, a large fraction of the internal space of such implantable medical devices may be consumed by a battery or other power source. As the battery life determines the potential useful life expectancy of the implantable medical device, there is a desire to make the batteries as large as possible within the confines of the available space.

What would be desirable is an implantable medical device that has recharge capability for recharging a rechargeable power source of the implantable medical device. This may give the implantable medical device a longer useful life expectancy and/or may not require as much battery space permitting a significantly smaller device size. A smaller device size may make the device more easily deliverable and implantable in the body, allow the device to be implantable in smaller and more confined spaces in the body, and/or may make the device less expensive to produce.

SUMMARY

The disclosure is directed to implantable medical that provide a long lasting power source often within a smaller device housing. While a leadless cardiac pacemaker is used as an example implantable medical device, the disclosure may be applied to any suitable implantable medical device including, for example, neuro-stimulators, diagnostic devices including those that do not deliver therapy, and/or any other suitable implantable medical device as desired.

In some cases, the disclosure pertains to implantable medical devices (IMD) such as leadless cardiac pacemakers (LCP) that include a rechargeable power source such as a rechargeable battery, a rechargeable capacitor or a rechargeable supercapacitor. In some cases, the IMD may include a plurality of receiving coils that may capture a non-radiative near-field energy and then convert the near-field energy into electrical energy that may be used to recharge the rechargeable power source. Accordingly, since the rechargeable power source does not have to maintain sufficient energy stores in a single charge for the entire expected life of the IMD, the power source itself and thus the IMD may be made smaller while still meeting device longevity expectations.

In an example of the disclosure, an implantable medical device (IMD) may be configured to be implanted within a patient and may include a housing configured for trans-catheter deployment. A plurality of electrodes may be exposed external to the housing. Therapeutic circuitry may be disposed within the housing and operatively coupled to the plurality of electrodes and configured to sense one or more signals via one or more of the plurality of electrodes and/or to stimulate tissue via one or more of the plurality of electrodes. A rechargeable power source may be disposed within the housing and configured to power the therapeutic circuitry. A plurality of receiving coils configured to receive non-radiative near-field energy through the patient's body, wherein each of the plurality of receiving coils has a primary capture axis along which a maximum amount of non-radiative near-field energy is captured, and wherein at least one of the plurality of receiving coils has a primary capture axis that is non-parallel with the primary capture axis of another one of the plurality of receiving coils. Charging circuitry may be operatively coupled with the plurality of receiving coils and the rechargeable power source, the charging circuitry may be configured to use the non-radiative near-field energy received via the plurality of receiving coils to charge the rechargeable power source.

Alternatively or additionally to any of the embodiments above, at least two of the plurality of receiving coils may be operatively coupled in a power summation configuration.

Alternatively or additionally to any of the embodiments above, at least one of the plurality of receiving coils may be disposed outside the housing.

Alternatively or additionally to any of the embodiments above, at least one of the plurality of receiving coils may be disposed within the housing.

Alternatively or additionally to any of the embodiments above, a ratio of a length of the at least one of the plurality of receiving coils to a diameter of the at least one of the plurality of receiving coils may be greater than or equal to 3 to 1 and the at least one of the plurality of receiving coils may have a ferrite core.

Alternatively or additionally to any of the embodiments above, the charging circuitry may be further configured to select one of the plurality of receiving coils and to receive non-radiative near-field energy using the selected receiving coil, monitor the non-radiative near-field energy received via the selected receiving coil and detect a predetermined condition, and in response to detecting the predetermined condition, select a different one of the plurality of receiving coils and receive non-radiative near-field energy using the different one of the plurality of receiving coils.

Alternatively or additionally to any of the embodiments above, at least one of the plurality of receiving coils may be non-planar and form a three-dimensional surface.

Alternatively or additionally to any of the embodiments above, a maximum outer dimension of at least one of the plurality of receiving coils may be less than 1/10 of the wavelength of an applied magnetic field supplying the non-radiative near-field energy. the applied magnetic field may have a frequency that is greater than or equal to 10 kHz and less than or equal to 100 MHz.

Alternatively or additionally to any of the embodiments above, the plurality of receiving coils may be further configured to establish an inductive communication link with an external device.

Alternatively or additionally to any of the embodiments above, the IMD may be a leadless cardiac pacemaker (LCP).

Alternatively or additionally to any of the embodiments above, one of the plurality of electrodes may be carried by a first remote electrode unit that is remote from but tethered relative to the housing and may include a fixation structure for fixing the first remote electrode unit at a first location in the patient, and the first remote electrode unit may carry one of the plurality of receiving coils. Furthermore, another one of the plurality of electrodes may be carried by a second remote electrode unit that is remote from but tethered relative to the housing and may include a fixation structure for fixing the second remote electrode unit at a second location in the patient, and the second remote electrode unit may carry another one of the plurality of receiving coils.

In another example of the disclosure, an implantable medical device (IMD) may be configured to be implanted within a patient's body and may include one or more sensors. Circuitry may be operatively coupled to the one or more sensors. A rechargeable power source may power the circuitry. A plurality of receiving coils may be configured to receive non-radiative near-field energy through the patient's body, the plurality of receiving coils may be operatively coupled in a power summing configuration, wherein each of the plurality of receiving coils may have a primary capture axis along which a maximum amount of non-radiative near-field energy is captured, and wherein at least one of the plurality of receiving coils may have a primary capture axis that is non-parallel with the primary capture axis of another one of the plurality of receiving coils. Charging circuitry may be operatively coupled with the plurality of receiving coils and the rechargeable power source, and may be configured to use the non-radiative near-field energy received via the plurality of receiving coils to charge the rechargeable power source.

Alternatively or additionally to any of the embodiments above, at least one of the plurality of receiving coils may have a ferrite core.

Alternatively or additionally to any of the embodiments above, a ratio of a length of at least one of the plurality of receiving coils to a diameter of the at least one of the plurality of receiving coils may be greater than or equal to 2 to 1.

Alternatively or additionally to any of the embodiments above, the IMD may further comprise a flexible substrate that may be configured to conform to a surface (e.g. endocardial, epicardial, septal, free wall) of the patient's heart, and the one or more sensors, the circuitry, the rechargeable power source, the plurality of receiving coils and the charging circuitry may be mounted to the flexible substrate.

Alternatively or additionally to any of the embodiments above, the IMD may further comprise a flexible substrate that may be configured to conform to a surface of a patient, and at least two of the plurality of receiving coils may be fixed to the flexible substrate.

In another example of the disclosure, an implantable medical device (IMD) may be configured to be implanted within a patient's body and may include a housing configured for trans-catheter deployment. A plurality of electrodes may be exposed external to the housing. Therapeutic circuitry may be disposed within the housing and may be operatively coupled to the plurality of electrodes and configured to sense one or more signals via one or more of the plurality of electrodes and/or to stimulate tissue via one or more of the plurality of electrodes. A rechargeable power source may be disposed within the housing and may be configured to power the therapeutic circuitry. A plurality of receiving coils may be disposed outside the housing and may be operatively coupled to the rechargeable power source, and may be configured to receive non-radiative near-field energy through the patient's body, and move from a pre-deployment compressed state to an expanded post-deployment state, wherein in the post-deployment state of each of the plurality of receiving coils may have a primary capture axis along which a maximum amount of non-radiative near-field energy is captured, and wherein at least one of the plurality of receiving coils may have a primary capture axis that is non-parallel with the primary capture axis of another one of the plurality of receiving coils. Charging circuitry may be operatively coupled with the plurality of receiving coils and the rechargeable power source, and may be configured to use the non-radiative near-field energy received via the plurality of receiving coils to charge the rechargeable power source.

Alternatively or additionally to any of the embodiments above, at least two of the plurality of receiving coils may be operatively coupled in a power summation configuration.

Alternatively or additionally to any of the embodiments above, a maximum outer dimension of at least one of the plurality of receiving coils may be less than 1/10 of the wavelength of an applied magnetic field supplying the non-radiative near-field energy, and wherein the applied magnetic field supplying the non-radiative near-field energy may have a frequency that is greater than or equal to 10 kHz and less than or equal to 100 MHz.

Alternatively or additionally to any of the embodiments above, the IMD is a leadless cardiac pacemaker (LCP).

The above summary of some illustrative embodiments is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The Figures and Description which follow more particularly exemplify these and other illustrative embodiments.

BRIEF DESCRIPTION OF THE FIGURES

The disclosure may be more completely understood in consideration of the following description in connection with the accompanying drawings, in which:

FIG. 1 is a schematic block diagram of an illustrative LCP in accordance with an example of the disclosure;

FIG. 2 is a schematic block diagram of another illustrative medical device that may be used in conjunction with the LCP of FIG. 1;

FIG. 3 is a schematic diagram of an exemplary medical system that includes multiple LCPs and/or other devices in communication with one another;

FIG. 4 is a schematic diagram of a system including an LCP and another medical device, in accordance with an example of the disclosure;

FIG. 5 is a side view of an illustrative implantable leadless cardiac device;

FIG. 6 is a schematic diagram of a patient including a rechargeable implantable medical device system;

FIG. 7 is a schematic of an illustrative circuit for a coupled inductor system;

FIG. 8 is a schematic of an illustrative coupled inductor power summation system;

FIG. 9 is a schematic diagram of an illustrative implantable medical device (IMD) according to an example of the disclosure;

FIG. 10 is a schematic diagram of another illustrative IMD according to an example of the disclosure;

FIG. 11 is a schematic diagram of another illustrative IMD according to an example of the disclosure;

FIG. 12 is a cross-sectional side view of an illustrative IMD according to an example of the disclosure;

FIG. 13 is a cross-sectional side view of another illustrative IMD according to an example of the disclosure;

FIG. 14 is a cross-sectional side view of another illustrative IMD according to an example of the disclosure;

FIG. 15 is a cross-sectional side view of another illustrative IMD according to an example of the disclosure;

FIG. 16A-16D is an illustrative delivery device that may be used to deliver an illustrative IMD in a chamber of a heart according to an example of the disclosure; and

FIG. 17A-17D is an illustrative delivery device that may be used to deliver an illustrative IMD in a chamber of a heart according to an example of the disclosure.

While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the disclosure to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure.

DESCRIPTION

For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification.

All numeric values are herein assumed to be modified by the term “about,” whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the terms “about” may include numbers that are rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).

As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

It is noted that references in the specification to “an embodiment”, “some embodiments”, “other embodiments”, etc., indicate that the embodiment described may include one or more particular features, structures, and/or characteristics. However, such recitations do not necessarily mean that all embodiments include the particular features, structures, and/or characteristics. Additionally, when particular features, structures, and/or characteristics are described in connection with one embodiment, it should be understood that such features, structures, and/or characteristics may also be used connection with other embodiments whether or not explicitly described unless clearly stated to the contrary.

The following description should be read with reference to the drawings in which similar structures in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the disclosure.

FIG. 1 depicts an illustrative leadless cardiac pacemaker (LCP) that may be implanted into a patient and may operate to deliver appropriate therapy to the heart, such as to deliver anti-tachycardia pacing (ATP) therapy, cardiac resynchronization therapy (CRT), bradycardia therapy, and/or the like. While a leadless cardiac pacemaker (LCP) is used as an example implantable medical device, it is contemplated that the concepts disclosed herein can be applied to any suitable implantable medical device (a therapeutic device, a diagnostic device, a cardiac stimulator, a neural stimulator). As can be seen in FIG. 1, the LCP 100 may be a compact device with all components housed within or directly on a housing 120. In some cases, the LCP 100 may be considered as being an example of an implantable medical device (IMD). In the example shown in FIG. 1, the LCP 100 may include a communication module 102, a pulse generator module 104, an electrical sensing module 106, a mechanical sensing module 108, a processing module 110, a battery 112, and an electrode arrangement 114. The LCP 100 may include more or less modules, depending on the application.

The communication module 102 may be configured to communicate with devices such as sensors, other medical devices such as an SICD, and/or the like, that are located externally to the LCP 100. Such devices may be located either external or internal to the patient's body. Irrespective of the location, external devices (i.e. external to the LCP 100 but not necessarily external to the patient's body) can communicate with the LCP 100 via communication module 102 to accomplish one or more desired functions. For example, the LCP 100 may communicate information, such as sensed electrical signals, data, instructions, messages, R-wave detection markers, etc., to an external medical device (e.g. SICD and/or programmer) through the communication module 102. The external medical device may use the communicated signals, data, instructions, messages, R-wave detection markers, etc., to perform various functions, such as determining occurrences of arrhythmias, delivering electrical stimulation therapy, storing received data, and/or performing any other suitable function. The LCP 100 may additionally receive information such as signals, data, instructions and/or messages from the external medical device through the communication module 102, and the LCP 100 may use the received signals, data, instructions and/or messages to perform various functions, such as determining occurrences of arrhythmias, delivering electrical stimulation therapy, storing received data, and/or performing any other suitable function. The communication module 102 may be configured to use one or more methods for communicating with external devices. For example, the communication module 102 may communicate via radiofrequency (RF) signals, inductive coupling, optical signals, acoustic signals, conducted communication signals, and/or any other signals suitable for communication.

In the example shown in FIG. 1, the pulse generator module 104 may be electrically connected to the electrodes 114. In some examples, the LCP 100 may additionally include electrodes 114′. In such examples, the pulse generator 104 may also be electrically connected to the electrodes 114′. The pulse generator module 104 may be configured to generate electrical stimulation signals. For example, the pulse generator module 104 may generate and deliver electrical stimulation signals by using energy stored in the battery 112 within the LCP 100 and deliver the generated electrical stimulation signals via the electrodes 114 and/or 114′. Alternatively, or additionally, the pulse generator 104 may include one or more capacitors, and the pulse generator 104 may charge the one or more capacitors by drawing energy from the battery 112. The pulse generator 104 may then use the energy of the one or more capacitors to deliver the generated electrical stimulation signals via the electrodes 114 and/or 114′. In at least some examples, the pulse generator 104 of the LCP 100 may include switching circuitry to selectively connect one or more of the electrodes 114 and/or 114′ to the pulse generator 104 in order to select which of the electrodes 114/114′ (and/or other electrodes) the pulse generator 104 delivers the electrical stimulation therapy. The pulse generator module 104 may generate and deliver electrical stimulation signals with particular features or in particular sequences in order to provide one or multiple of a number of different stimulation therapies. For example, the pulse generator module 104 may be configured to generate electrical stimulation signals to provide electrical stimulation therapy to combat bradycardia, tachycardia, cardiac synchronization, bradycardia arrhythmias, tachycardia arrhythmias, fibrillation arrhythmias, cardiac synchronization arrhythmias and/or to produce any other suitable electrical stimulation therapy. Some more common electrical stimulation therapies include anti-tachycardia pacing (ATP) therapy, cardiac resynchronization therapy (CRT), and cardioversion/defibrillation therapy. In some cases, the pulse generator 104 may provide a controllable pulse energy. In some cases, the pulse generator 104 may allow the controller to control the pulse voltage, pulse width, pulse shape or morphology, and/or any other suitable pulse characteristic.

In some examples, the LCP 100 may include an electrical sensing module 106, and in some cases, a mechanical sensing module 108. The electrical sensing module 106 may be configured to sense the cardiac electrical activity of the heart. For example, the electrical sensing module 106 may be connected to the electrodes 114/114′, and the electrical sensing module 106 may be configured to receive cardiac electrical signals conducted through the electrodes 114/114′. The cardiac electrical signals may represent local information from the chamber in which the LCP 100 is implanted. For instance, if the LCP 100 is implanted within a ventricle of the heart (e.g. RV, LV), cardiac electrical signals sensed by the LCP 100 through the electrodes 114/114′ may represent ventricular cardiac electrical signals. In some cases, the LCP 100 may be configured to detect cardiac electrical signals from other chambers (e.g. far field), such as the P-wave from the atrium.

The mechanical sensing module 108 may include one or more sensors, such as an accelerometer, a pressure sensor, a heart sound sensor, a blood-oxygen sensor, a chemical sensor, a temperature sensor, a flow sensor and/or any other suitable sensors that are configured to measure one or more mechanical/chemical parameters of the patient. Both the electrical sensing module 106 and the mechanical sensing module 108 may be connected to a processing module 110, which may provide signals representative of the sensed mechanical parameters. Although described with respect to FIG. 1 as separate sensing modules, in some cases, the electrical sensing module 106 and the mechanical sensing module 108 may be combined into a single sensing module, as desired.

The electrodes 114/114′ can be secured relative to the housing 120 but exposed to the tissue and/or blood surrounding the LCP 100. In some cases, the electrodes 114 may be generally disposed on either end of the LCP 100 and may be in electrical communication with one or more of the modules 102, 104, 106, 108, and 110. The electrodes 114/114′ may be supported by the housing 120, although in some examples, the electrodes 114/114′ may be connected to the housing 120 through short connecting wires such that the electrodes 114/114′ are not directly secured relative to the housing 120. In examples where the LCP 100 includes one or more electrodes 114′, the electrodes 114′ may in some cases be disposed on the sides of the LCP 100, which may increase the number of electrodes by which the LCP 100 may sense cardiac electrical activity, deliver electrical stimulation and/or communicate with an external medical device. The electrodes 114/114′ can be made up of one or more biocompatible conductive materials such as various metals or alloys that are known to be safe for implantation within a human body. In some instances, the electrodes 114/114′ connected to the LCP 100 may have an insulative portion that electrically isolates the electrodes 114/114′ from adjacent electrodes, the housing 120, and/or other parts of the LCP 100. In some cases, one or more of the electrodes 114/114′ may be provided on a tail (not shown) that extends away from the housing 120.

The processing module 110 can be configured to control the operation of the LCP 100. For example, the processing module 110 may be configured to receive electrical signals from the electrical sensing module 106 and/or the mechanical sensing module 108. Based on the received signals, the processing module 110 may determine, for example, abnormalities in the operation of the heart H. Based on any determined abnormalities, the processing module 110 may control the pulse generator module 104 to generate and deliver electrical stimulation in accordance with one or more therapies to treat the determined abnormalities. The processing module 110 may further receive information from the communication module 102. In some examples, the processing module 110 may use such received information to help determine whether an abnormality is occurring, determine a type of abnormality, and/or to take particular action in response to the information. The processing module 110 may additionally control the communication module 102 to send/receive information to/from other devices.

In some examples, the processing module 110 may include a pre-programmed chip, such as a very-large-scale integration (VLSI) chip and/or an application specific integrated circuit (ASIC). In such embodiments, the chip may be pre-programmed with control logic in order to control the operation of the LCP 100. By using a pre-programmed chip, the processing module 110 may use less power than other programmable circuits (e.g. general purpose programmable microprocessors) while still being able to maintain basic functionality, thereby potentially increasing the battery life of the LCP 100. In other examples, the processing module 110 may include a programmable microprocessor. Such a programmable microprocessor may allow a user to modify the control logic of the LCP 100 even after implantation, thereby allowing for greater flexibility of the LCP 100 than when using a pre-programmed ASIC. In some examples, the processing module 110 may further include a memory, and the processing module 110 may store information on and read information from the memory. In other examples, the LCP 100 may include a separate memory (not shown) that is in communication with the processing module 110, such that the processing module 110 may read and write information to and from the separate memory.

The battery 112 may provide power to the LCP 100 for its operations. In some instances, the battery 112 may a rechargeable battery, which may help increase the useable lifespan of the LCP 100. In still other examples, the battery 112 may be some other type of power source, as desired.

To implant the LCP 100 inside a patient's body, an operator (e.g., a physician, clinician, etc.), may fix the LCP 100 to the cardiac tissue of the patient's heart. To facilitate fixation, the LCP 100 may include one or more anchors 116. The anchor 116 may include any one of a number of fixation or anchoring mechanisms. For example, the anchor 116 may include one or more pins, staples, threads, screws, helix, tines, and/or the like. In some examples, although not shown, the anchor 116 may include threads on its external surface that may run along at least a partial length of the anchor 116. The threads may provide friction between the cardiac tissue and the anchor to help fix the anchor 116 within the cardiac tissue. In other examples, the anchor 116 may include other structures such as barbs, spikes, or the like to facilitate engagement with the surrounding cardiac tissue.

FIG. 2 depicts an example of another or second medical device (MD) 200, which may be used in conjunction with the LCP 100 (FIG. 1) in order to detect and/or treat cardiac abnormalities. In some cases, the MD 200 may be considered as an example of the IMD and/or the LCP. In the example shown, the MD 200 may include a communication module 202, a pulse generator module 204, an electrical sensing module 206, a mechanical sensing module 208, a processing module 210, and a battery 218. Each of these modules may be similar to the modules 102, 104, 106, 108, and 110 of LCP 100. Additionally, the battery 218 may be similar to the battery 112 of the LCP 100. In some examples, however, the MD 200 may have a larger volume within the housing 220. In such examples, the MD 200 may include a larger battery and/or a larger processing module 210 capable of handling more complex operations than the processing module 110 of the LCP 100.

While it is contemplated that the MD 200 may be another leadless device such as shown in FIG. 1, in some instances the MD 200 may include leads such as leads 212. The leads 212 may include electrical wires that conduct electrical signals between the electrodes 214 and one or more modules located within the housing 220. In some cases, the leads 212 may be connected to and extend away from the housing 220 of the MD 200. In some examples, the leads 212 are implanted on, within, or adjacent to a heart of a patient. The leads 212 may contain one or more electrodes 214 positioned at various locations on the leads 212, and in some cases at various distances from the housing 220. Some leads 212 may only include a single electrode 214, while other leads 212 may include multiple electrodes 214. Generally, the electrodes 214 are positioned on the leads 212 such that when the leads 212 are implanted within the patient, one or more of the electrodes 214 are positioned to perform a desired function. In some cases, the one or more of the electrodes 214 may be in contact with the patient's cardiac tissue. In some cases, the one or more of the electrodes 214 may be positioned subcutaneously and outside of the patient's heart. In some cases, the electrodes 214 may conduct intrinsically generated electrical signals to the leads 212, e.g. signals representative of intrinsic cardiac electrical activity. The leads 212 may, in turn, conduct the received electrical signals to one or more of the modules 202, 204, 206, and 208 of the MD 200. In some cases, the MD 200 may generate electrical stimulation signals, and the leads 212 may conduct the generated electrical stimulation signals to the electrodes 214. The electrodes 214 may then conduct the electrical signals and delivery the signals to the patient's heart (either directly or indirectly).

The mechanical sensing module 208, as with the mechanical sensing module 108, may contain or be electrically connected to one or more sensors, such as accelerometers, acoustic sensors, blood pressure sensors, heart sound sensors, blood-oxygen sensors, and/or other sensors which are configured to measure one or more mechanical/chemical parameters of the heart and/or patient. In some examples, one or more of the sensors may be located on the leads 212, but this is not required. In some examples, one or more of the sensors may be located in the housing 220.

While not required, in some examples, the MD 200 may be an implantable medical device. In such examples, the housing 220 of the MD 200 may be implanted in, for example, a transthoracic region of the patient. The housing 220 may generally include any of a number of known materials that are safe for implantation in a human body and may, when implanted, hermetically seal the various components of the MD 200 from fluids and tissues of the patient's body.

In some cases, the MD 200 may be an implantable cardiac pacemaker (ICP). In this example, the MD 200 may have one or more leads, for example the leads 212, which are implanted on or within the patient's heart. The one or more leads 212 may include one or more electrodes 214 that are in contact with cardiac tissue and/or blood of the patient's heart. The MD 200 may be configured to sense intrinsically generated cardiac electrical signals and determine, for example, one or more cardiac arrhythmias based on analysis of the sensed signals. The MD 200 may be configured to deliver CRT, ATP therapy, bradycardia therapy, and/or other therapy types via the leads 212 implanted within the heart. In some examples, the MD 200 may additionally be configured provide defibrillation therapy.

In some instances, the MD 200 may be an implantable cardioverter-defibrillator (ICD). In such examples, the MD 200 may include one or more leads implanted within a patient's heart. The MD 200 may also be configured to sense cardiac electrical signals, determine occurrences of tachyarrhythmias based on the sensed signals, and may be configured to deliver defibrillation therapy in response to determining an occurrence of a tachyarrhythmia. In other examples, the MD 200 may be a subcutaneous implantable cardioverter-defibrillator (S-ICD). In examples where the MD 200 is an S-ICD, one of the leads 212 may be a subcutaneously implanted lead. In at least some examples where the MD 200 is an S-ICD, the MD 200 may include only a single lead which is implanted subcutaneously, but this is not required. In some instances, the lead(s) may have one or more electrodes that are placed subcutaneously and outside of the chest cavity. In other examples, the lead(s) may have one or more electrodes that are placed inside of the chest cavity, such as just interior of the sternum but outside of the heart H.

In some examples, the MD 200 may not be an implantable medical device. Rather, the MD 200 may be a device external to the patient's body, and may include skin-electrodes that are placed on a patient's body. In such examples, the MD 200 may be able to sense surface electrical signals (e.g. cardiac electrical signals that are generated by the heart or electrical signals generated by a device implanted within a patient's body and conducted through the body to the skin). In such examples, the MD 200 may be configured to deliver various types of electrical stimulation therapy, including, for example, defibrillation therapy.

FIG. 3 illustrates an example of a medical device system and a communication pathway through which multiple medical devices 302, 304, 306, and/or 310 may communicate. In the example shown, the medical device system 300 may include LCPs 302 and 304, external medical device 306, and other sensors/devices 310. The external device 306 may be any of the devices described previously with respect to the MD 200. Other sensors/devices 310 may also be any of the devices described previously with respect to the MD 200. In some instances, other sensors/devices 310 may include a sensor, such as an accelerometer, an acoustic sensor, a blood pressure sensor, or the like. In some cases, other sensors/devices 310 may include an external programmer device that may be used to program one or more devices of the system 300.

Various devices of the system 300 may communicate via communication pathway 308. For example, the LCPs 302 and/or 304 may sense intrinsic cardiac electrical signals and may communicate such signals to one or more other devices 302/304, 306, and 310 of the system 300 via communication pathway 308. In one example, one or more of the devices 302/304 may receive such signals and, based on the received signals, determine an occurrence of an arrhythmia. In some cases, the device or devices 302/304 may communicate such determinations to one or more other devices 306 and 310 of the system 300. In some cases, one or more of the devices 302/304, 306, and 310 of the system 300 may take action based on the communicated determination of an arrhythmia, such as by delivering a suitable electrical stimulation to the heart of the patient. It is contemplated that the communication pathway 308 may communicate using RF signals, inductive coupling, optical signals, acoustic signals, or any other signals suitable for communication. Additionally, in at least some examples, device communication pathway 308 may include multiple signal types. For instance, other sensors/device 310 may communicate with the external device 306 using a first signal type (e.g. RF communication) but communicate with the LCPs 302/304 using a second signal type (e.g. conducted communication). Further, in some examples, communication between devices may be limited. For instance, as described above, in some examples, the LCPs 302/304 may communicate with the external device 306 only through other sensors/devices 310, where the LCPs 302/304 send signals to other sensors/devices 310, and other sensors/devices 310 relay the received signals to the external device 306.

In some cases, the communication pathway 308 may include conducted communication. Accordingly, devices of the system 300 may have components that allow for such conducted communication. For instance, the devices of system 300 may be configured to transmit conducted communication signals (e.g. current and/or voltage pulses) into the patient's body via one or more electrodes of a transmitting device, and may receive the conducted communication signals (e.g. pulses) via one or more electrodes of a receiving device. The patient's body may “conduct” the conducted communication signals (e.g. pulses) from the one or more electrodes of the transmitting device to the electrodes of the receiving device in the system 300. In such examples, the delivered conducted communication signals (e.g. pulses) may differ from pacing or other therapy signals. For example, the devices of the system 300 may deliver electrical communication pulses at an amplitude/pulse width that is sub-capture threshold to the heart. Although, in some cases, the amplitude/pulse width of the delivered electrical communication pulses may be above the capture threshold of the heart, but may be delivered during a blanking period of the heart (e.g. refractory period) and/or may be incorporated in or modulated onto a pacing pulse, if desired.

Delivered electrical communication pulses may be modulated in any suitable manner to encode communicated information. In some cases, the communication pulses may be pulse width modulated or amplitude modulated. Alternatively, or in addition, the time between pulses may be modulated to encode desired information. In some cases, conducted communication pulses may be voltage pulses, current pulses, biphasic voltage pulses, biphasic current pulses, or any other suitable electrical pulse as desired.

FIG. 4 shows an illustrative medical device system. In FIG. 4, an LCP 402 is shown fixed to the interior of the left ventricle of the heart 410, and a pulse generator 406 is shown coupled to a lead 412 having one or more electrodes 408 a-408 c. In some cases, the pulse generator 406 may be part of a subcutaneous implantable cardioverter-defibrillator (S-ICD), and the one or more electrodes 408 a-408 c may be positioned subcutaneously. In some cases, the one or more electrodes 408 a-408 c may be placed inside of the chest cavity but outside of the heart, such as just interior of the sternum.

In some cases, the LCP 402 may communicate with the subcutaneous implantable cardioverter-defibrillator (S-ICD). In some cases, the lead 412 and/or pulse generator 406 may include an accelerometer 414 that may, for example, be configured to sense vibrations that may be indicative of heart sounds.

In some cases, the LCP 402 may be in the right ventricle, right atrium, left ventricle or left atrium of the heart, as desired. In some cases, more than one LCP 402 may be implanted. For example, one LCP may be implanted in the right ventricle and another may be implanted in the right atrium. In another example, one LCP may be implanted in the right ventricle and another may be implanted in the left ventricle. In yet another example, one LCP may be implanted in each of the chambers of the heart.

FIG. 5 is a side view of an illustrative implantable leadless cardiac pacemaker (LCP) 610. The LCP 610 may be similar in form and function to the LCP 100 described above. The LCP 610 may include any of the modules and/or structural features described above with respect to the LCP 100 described above. The LCP 610 may include a shell or housing 612 having a proximal end 614 and a distal end 616. The illustrative LCP 610 includes a first electrode 620 secured relative to the housing 612 and positioned adjacent to the distal end 616 of the housing 612 and a second electrode 622 secured relative to the housing 612 and positioned adjacent to the proximal end 614 of the housing 612. The electrodes 620, 622 may be sensing and/or pacing electrodes to provide electro-therapy and/or sensing capabilities. The first electrode 620 may be capable of being positioned against or may otherwise contact the cardiac tissue of the heart while the second electrode 622 may be spaced away from the first electrode 620. The first and/or second electrodes 620, 622 may be exposed to the environment outside the housing 612 (e.g. to blood and/or tissue).

In some cases, the LCP 610 may include a pulse generator (e.g., electrical circuitry) and a power source (e.g., a battery, supercapacitor and/or other power source) within the housing 612 to provide electrical signals to the electrodes 620, 622 to control the pacing/sensing electrodes 620, 622. While not explicitly shown, the LCP 610 may also include, a communications module, an electrical sensing module, a mechanical sensing module, and/or a processing module, and the associated circuitry, similar in form and function to the modules 102, 106, 108, 110 described above. The various modules and electrical circuitry may be disposed within the housing 612. Electrical connections between the pulse generator and the electrodes 620, 622 may allow electrical stimulation to heart tissue and/or sense a physiological condition.

In the example shown, the LCP 610 includes a fixation mechanism 624 proximate the distal end 616 of the housing 612. The fixation mechanism 624 is configured to attach the LCP 610 to a wall of the heart H, or otherwise anchor the LCP 610 to the anatomy of the patient. In some instances, the fixation mechanism 624 may include one or more, or a plurality of hooks or tines 626 anchored into the cardiac tissue of the heart H to attach the LCP 610 to a tissue wall. In other instances, the fixation mechanism 624 may include one or more, or a plurality of passive tines, configured to entangle with trabeculae within the chamber of the heart H and/or a helical fixation anchor configured to be screwed into a tissue wall to anchor the LCP 610 to the heart H. These are just examples.

The LCP 610 may further include a docking member 630 proximate the proximal end 614 of the housing 612. The docking member 630 may be configured to facilitate delivery and/or retrieval of the LCP 610. For example, the docking member 630 may extend from the proximal end 614 of the housing 612 along a longitudinal axis of the housing 612. The docking member 630 may include a head portion 632 and a neck portion 634 extending between the housing 612 and the head portion 632. The head portion 632 may be an enlarged portion relative to the neck portion 634. For example, the head portion 632 may have a radial dimension from the longitudinal axis of the LCP 610 that is greater than a radial dimension of the neck portion 634 from the longitudinal axis of the LCP 610. In some cases, the docking member 630 may further include a tether retention structure 636 extending from or recessed within the head portion 632. The tether retention structure 636 may define an opening 638 configured to receive a tether or other anchoring mechanism therethrough. While the retention structure 636 is shown as having a generally “U-shaped” configuration, the retention structure 636 may take any shape that provides an enclosed perimeter surrounding the opening 638 such that a tether may be securably and releasably passed (e.g. looped) through the opening 638. In some cases, the retention structure 636 may extend though the head portion 632, along the neck portion 634, and to or into the proximal end 614 of the housing 612. The docking member 630 may be configured to facilitate delivery of the LCP 610 to the intracardiac site and/or retrieval of the LCP 610 from the intracardiac site. While this describes one example docking member 630, it is contemplated that the docking member 630, when provided, can have any suitable configuration.

It is contemplated that the LCP 610 may include one or more pressure sensors 640 coupled to or formed within the housing 612 such that the pressure sensor(s) is exposed to the environment outside the housing 612 to measure blood pressure within the heart. For example, if the LCP 610 is placed in the left ventricle, the pressure sensor(s) 640 may measure the pressure within the left ventricle. If the LCP 610 is placed in another portion of the heart (such as one of the atriums or the right ventricle), the pressures sensor(s) may measure the pressure within that portion of the heart. The pressure sensor(s) 640 may include a MEMS device, such as a MEMS device with a pressure diaphragm and piezoresistors on the diaphragm, a piezoelectric sensor, a capacitor-Micro-machined Ultrasonic Transducer (cMUT), a condenser, a micro-monometer, or any other suitable sensor adapted for measuring cardiac pressure. The pressures sensor(s) 640 may be part of a mechanical sensing module described herein. It is contemplated that the pressure measurements obtained from the pressures sensor(s) 640 may be used to generate a pressure curve over cardiac cycles. The pressure readings may be taken in combination with impedance measurements (e.g. the impedance between electrodes 620 and 622) to generate a pressure-impedance loop for one or more cardiac cycles as will be described in more detail below. The impedance may be a surrogate for chamber volume, and thus the pressure-impedance loop may be representative for a pressure-volume loop for the heart H.

In some embodiments, the LCP 610 may be configured to measure impedance between the electrodes 620, 622. More generally, the impedance may be measured between other electrode pairs, such as the additional electrodes 114′ described above. In some cases, the impedance may be measure between two spaced LCP's, such as two LCP's implanted within the same chamber (e.g. LV) of the heart H, or two LCP's implanted in different chambers of the heart H (e.g. RV and LV). The processing module of the LCP 610 and/or external support devices may derive a measure of cardiac volume from intracardiac impedance measurements made between the electrodes 620, 622 (or other electrodes). Primarily due to the difference in the resistivity of blood and the resistivity of the cardiac tissue of the heart H, the impedance measurement may vary during a cardiac cycle as the volume of blood (and thus the volume of the chamber) surrounding the LCP changes. In some cases, the measure of cardiac volume may be a relative measure, rather than an actual measure. In some cases, the intracardiac impedance may be correlated to an actual measure of cardiac volume via a calibration process, sometimes performed during implantation of the LCP(s). During the calibration process, the actual cardiac volume may be determined using fluoroscopy or the like, and the measured impedance may be correlated to the actual cardiac volume.

In some cases, the LCP 610 may be provided with energy delivery circuitry operatively coupled to the first electrode 620 and the second electrode 622 for causing a current to flow between the first electrode 620 and the second electrode 622 in order to determine the impedance between the two electrodes 620, 622 (or other electrode pair). It is contemplated that the energy delivery circuitry may also be configured to deliver pacing pulses via the first and/or second electrodes 620, 622. The LCP 610 may further include detection circuitry operatively coupled to the first electrode 620 and the second electrode 622 for detecting an electrical signal received between the first electrode 620 and the second electrode 622. In some instances, the detection circuitry may be configured to detect cardiac signals received between the first electrode 620 and the second electrode 622.

When the energy delivery circuitry delivers a current between the first electrode 620 and the second electrode 622, the detection circuitry may measure a resulting voltage between the first electrode 620 and the second electrode 622 (or between a third and fourth electrode separate from the first electrode 620 and the second electrode 622, not shown) to determine the impedance. When the energy delivery circuitry delivers a voltage between the first electrode 620 and the second electrode 622, the detection circuitry may measure a resulting current between the first electrode 620 and the second electrode 622 (or between a third and fourth electrode separate from the first electrode 620 and the second electrode 622) to determine the impedance.

FIG. 6 provides a highly schematic illustration of a patient 700 having an implantable medical device 702 implanted within the patient 700. While the implantable medical device 702 is shown as being in or near the patient's chest, it will be appreciated that this is merely illustrative, as the implantable medical device 702, depending on functionality, may be implanted in other locations within the patient 700. A transmitter 704 is shown exterior to the patient 700. In some cases, the transmitter 704 may be configured to transmit reactive near-field energy that is of a wavelength (or frequency, as wavelength and frequency are related by the numerical speed of light) and intensity that can safety pass into the patient 700 to the implantable medical device 702 without causing excessive tissue heating and/or other potentially damaging effects to the patient 700.

The transmitter 704 may take any of a variety of forms. For example, while shown schematically as a box in FIG. 6, the transmitter 704 may be sized and configured for the patient 700 to periodically wear about their neck on a lanyard or in a shirt pocket, which would place the transmitter 704 proximate their chest, at about the same vertical and horizontal position as the implantable medical device 702 within the patient's chest. In some cases, for example, the transmitter 704 may be built into the back of a chair that the patient 700 would periodically sit in to recharge the implantable medical device 702. The chair may be in the patient's home, for a daily recharge, for example, or may be at a remote location such as a medical clinic, for a patient 700 having a longer recharge schedule. As another example, the transmitter 704 may be built into a bed such that the transmitter 704 may at least partially recharge the implantable medical device 702 each evening when the patient 700 sleeps. In some cases, the transmitter 704 may be configured to only transmit once per week, or once per month, for example, depending on the power requirements of the implantable medical device 702. In some cases, the transmitter 704 and the implantable medical device 702 may communicate with each other. When so provided, the implantable medical device 702 may report its current battery recharge level to the transmitter 704, and if the current battery recharge level is below a threshold, the transmitter 704 may transmit power to the implantable medical device 702. These are just examples.

It will be appreciated that the implantable medical device 702 may be configured to periodically or continuously receive near-field energy at a wavelength and intensity that is safe for the patient 700 and that the implantable medical device 702 may use to recharge a rechargeable power source within the implantable medical device 702. The near-field energy may be received at a rate that exceeds a rate at which power is being drawn from the rechargeable battery and consumed by various components within the implantable medical device 702.

FIG. 7 provides an illustrative circuit for a coupled inductor system 800. Inductive coupling is the near-field wireless transmission of electrical energy between a source 802 and a device 804. In some cases, the source 802 may transfer power from a source inductor 806 to a device inductor 808 by a magnetic field. The system 800, therefore, may act as a transformer. In some cases, a signal generator 810 may generate an alternating current (AC) through the source inductor 806 and create an oscillating magnetic field. The magnetic field may pass through the device inductor 808 and induce an alternating electromagnetic force (EMF), which creates an alternating current (AC) in the device 804. The induced AC may either drive a load 812 directly, or may be rectified to direct current (DC) by a rectifier (not shown) in the device 804, which may then drive the load 812.

In some cases, the power transferred may increase with frequency and mutual inductance between the source inductor 806 and the device inductor 808, which may depend on their geometry (e.g. orientation, size, shape, etc.) and the distance between them. For example, if the source inductor 806 and the device inductor 808 are on the same axis (i.e., a primary capture axis) and close together so a large percentage of the magnetic flux from the source inductor 806 passes through the device inductor 808, the transfer of power may approach 100%. The greater the separation between the coils, the more the magnetic field from the source inductor 806 may not interact with the device inductor 808, and the transfer of power may decrease.

In some cases, the source inductor 806 and/or the device inductor 808 may be fitted with magnetic cores. A magnetic core can be a piece of magnetic material with a high magnetic permeability used to confine and guide magnetic fields in electrical, electromechanical and magnetic devices such as electromagnets, transformers, generators, inductors, and other magnetic assemblies. In some cases, the magnetic core may be made of ferromagnetic metal such as iron, or ferromagnetic compounds such as ferrites. The high permeability, relative to the surrounding atmosphere, may cause the magnetic field lines to be concentrated in the ferrite core. In some cases, the use of the ferrite core can concentrate the strength and increase the effect of magnetic fields produced by electric currents through the source inductor 806. The magnetic field may also be confined and guided, using the ferrite cores, and may improve coupling, thus, improving the transfer of power.

In some cases, the system may achieve resonant inductive coupling. In this case, the source 802 can be tuned to resonant at the same frequency as the device 804. In some cases, the source 802 can include the source inductor 806 connected to a capacitor 814 as shown. A similar capacitor may be included in the device 804. A resonance between the source inductor 806 circuit and the device inductor 808 circuit can increase the coupling and power transfer between the devices. In some cases, when the system 800 achieves resonant inductive coupling, the source 802 and the device 804 may interact with each other more strongly than they do with non-resonant objects and power losses due to absorption in stray nearby objects may be reduced and/or negligible.

As discussed above, the power transfer efficiency may depend on the geometry (e.g. orientation, size, shape, etc.) of the source inductor 806 and the device inductor 808 (e.g., the direction of their primary capture axis) and the distance between them. In addition, in some cases, the impedance of a device may vary (e.g., due to aging of the circuitry of an IMD, due to the location of deployment of an IMD within a patient, etc.) and change the resonant frequency of the device. As a result, it may be difficult to achieve resonant inductive coupling over all conditions. To compensate for this, and in some cases, the source 802 and/or device 804 may include a tuning circuit that can be used to actively tune the resonance frequency of the source inductor circuit and/or device inductor circuit to help keep the devices in resonance. In some embodiments coupled inductor system 800 also provides an inductive mode of communication to support a communication pathway such as the communication pathway 308 shown in FIG. 3. The inductive communication link may be provided when the coupled inductor system 800 is not being utilized for transmission of electrical energy to recharge rechargeable power source 712. Alternatively the inductive communication link may be provided when the coupled inductor system 800 is being utilized for transmission of electrical energy to recharge rechargeable power source 712 via modulation of an transfer energy parameter (e.g. amplitude, frequency, phase, pulse width, etc.).

FIG. 8 provides an illustrative coupled inductor power summation system 900. In some cases, the power summation system 900 may be used to increase the overall power transferred from a source 902 to a device 904 by using two receiving inductors to capture the magnetic field induced by the source 902 and then power summing the captured energy. In some cases, a signal generator 906 may generate an AC through the source inductor 908 and create an oscillating magnetic field 910. Part of the source induced magnetic field 910 may pass through each of the two (or more) device inductors 912 and 914, which may induce an alternating EMF in the device inductors 912 and 914, and thus an AC in each of the device inductors 912 and 914. The AC produced by each of the device inductors 912 and 914 may be independently rectified by non-linear elements 918 and 920 (e.g., rectifying diodes), respectively, and the rectified currents may be summed together. The sum of the rectified currents may increase the total power delivered to the device load 916 relative to a system that has a single receiving device.

In this configuration, the power summation system 900 may reduce or avoid the power transfer inefficiencies caused by inductor geometries, the distance between the inductors, the changes in resonant frequency, and/or other factors. For example, in some cases, the magnetic field 910 may not pass directly through the device inductors 912 and 914. For instance, the direction of the primary capture axis of the device inductors 912 and 914 may not be completely aligned with the primary transfer axis of the source inductor 908. In such a case, when the primary capture axis of the device inductor 912 is aligned with the primary capture axis of the device inductor 914, and each receives the same component of the magnetic field 910, the two device inductors 912 and 914 may double the energy captured relative to a system with only a single device coil. When the primary capture axis of the device inductor 912 is miss-aligned with the primary capture axis of the device inductor 914, and each receives a different component of the magnetic field 910, one of the device inductors 912 and 914 may capture energy that i s not captured by the other of the device inductors 912 and 914. This may help capture a more consistent power level, particularly when the orientation between the source inductors 908 and the device inductors 912, and 914 is unknown or is changing over time.

Rather than having the device inductors 912 and 914 in a power summing configuration as shown in FIG. 8, it is contemplated that a switching circuit (not shown) may be used to individually select the device inductors 912 and 914. For example, the magnetic field 910 may pass directly through or almost directly through the device inductor 912 and may barely pass or not pass through the device inductor 914 (e.g., the direction of the primary capture axis of the device inductor 914 may not align with the primary transfer axis of the source inductor 908, there is a substantial distance between the device inductor 914 and the source inductor 908, etc.). In this case, the power contributed from the device inductor 914 may be negligible. The power summation system 900 may select only the device inductor 912 to inductively couple with the source inductor 908 and the power delivered to the device load 916 may be from the AC created by the alternating EMF in the device inductor 912. In some cases, the power summation system 900 may sample the AC created by each of the device inductors 912 and 914, and determine which of the coils to select. In some cases, the power summation system 900 may include a posture sensor and may select the coils based, at least in part, on the posture of the patient. In some cases, the power summation system 900 may include a respiration sensor and may select the coils based, at least in part, on a respiration parameter (e.g. respiration phase) of the patient. In some cases, the power summation system 900 may include an ECG sensor and may select the coils based, at least in part, on a cardiac (e.g. cardiac phase) of the patient. These are just examples.

In some cases, the source inductor 908 and/or the device inductors 912, and 914 may be fitted with ferrite cores. In these cases, the magnetic field created by the source inductor 908 may be increased, confined, and guided through the device inductors 912 and 914. As a result, the coupling between the source inductor 908 and the device inductors 912 and 914 may be improved, which may improve the overall transfer of power.

FIG. 9 provides an illustrative but non-limiting example of at least some of the components within the implantable medical device 702. In some cases, the implantable medical device 702 may include a device housing 706 that may encompass a receiving coil 708, charging circuitry 710, and a rechargeable power source 712. In various embodiments, the implantable medical device 702 may also include receiving coils 714 and 716. In certain embodiments, the receiving coils 714 and 716 may be external to the device housing 706.

The receiving coils 708, 714, and 716 may be any of a variety of different types of antennas. When considering the electromagnetic regions around a transmitting antenna, there are three categories, namely, (1) reactive near-field; (2) radiated near-field and (3) radiated far-field. The “Inductive” charging system of the present disclosure is intended to operate in the reactive near-field region. In inductive power systems, power is typically transferred over short distances by magnetic fields using inductive coupling between coils of wire, such as receiving coils 708, 714, and 716, or by electric fields using capacitive coupling between electrodes. In radiative power systems (e.g. radiated near-field and radiated far-field), power is typically transmitted by beams of electromagnetic (EM) energy. Radiative power systems can often transport energy for longer distances, but the ability of a receiving antenna to capture sufficient energy can be challenging, particular for applications where the size of the receiving antenna is limited.

In some cases, the transmitter 704 (FIG. 6) and implantable medical device 702 may inductively transfer power between about 10 kHz and 100 MHz within the patient's body. When so provided, the system operates in the reactive near-field (as in inductive charging system). In some cases, the transmitter 704 may transmit the near-field energy such that multiple implanted receiving coils (i.e., receiving coils 708, 714, and 716) may simultaneously or sequentially capture the near-field energy and provide it to the charging circuitry 710.

In some cases, the charging circuitry 710 may be configured to convert the received near-field energy into a form that may be used to recharge the rechargeable power source 712. In some instances, the charging circuitry 710 may function to recharge the rechargeable power source 712, and the implantable medical device 702 may include other circuitry (not shown) to provide other functions ascribed to the implantable medical device 702. In some cases, the charging circuitry 710 may provide power directly to circuitry (not shown) of the implantable medical device 702, such as sensing circuitry, therapy delivery circuitry, communication circuitry, and/or any other suitable circuitry.

The rechargeable power source 712 may include any type of rechargeable battery. In some cases, the rechargeable power source 712 may include a supercapacitor. The rechargeable power source 712 may take a three dimensional shape that facilitates incorporation of the rechargeable power source into the device housing 706. As will be appreciated, in some cases the device housing 706 may have a cylindrical or substantially cylindrical shape, in which case the rechargeable power source 712 may have a cylindrical or annular profile, such as a button battery or an elongated (in length) battery having a substantially cylindrical shape, but this is not required. In some cases, device housing 706 may be rigid; in some cases it may be flexible. It is recognized that there are possible tradeoffs in rechargeable battery shape and dimensions relative to performance, so these issues should be considered in designing the rechargeable power source 712 for a particular use. While FIG. 9 schematically shows a single rechargeable power source 712, in some cases there may be two, three or more distinct rechargeable power sources 712, each electrically coupled with the charging circuitry 710. For example, in some cases there may be performance advantages in having multiple rechargeable power sources 712. In some instances, there may be packaging advantages to having multiple (and smaller) rechargeable power sources 712. In some cases, rechargeable power source 712 may include more than one type of rechargeable power sources (e.g. both a rechargeable battery and a super capacitor).

FIG. 10 provides a schematic view of an illustrative IMD 1102 that may be configured to be implanted within a patient such as the patient 700 (FIG. 6). In some cases, electrodes 1110 a-1110 b may be exposed external to a housing 1118 and may be operably coupled to therapeutic circuitry 1108. While two electrodes are illustrated, it will be appreciated that in some instances the IMD 1102 may include three, four or more distinct electrodes. Depending on the intended functionality of the IMD 1102, the electrodes 1110 a-1110 b may be used for sensing and/or pacing the patient's heart. In some instances, for example, the IMD 1102 may be a leadless cardiac pacemaker (LCP), an implantable monitoring device or an implantable sensor. In some cases, the electrodes 1110 a-1110 b may be used for communicating with other implanted devices and/or with external devices. In some cases, communication with other implanted devices may include conductive communication, but this is not required. Rechargeable power source 1106 may be disposed within the housing 1118 and may be configured to power the IMD 1102, including the therapeutic circuitry 1108.

According to various embodiments, the housing 1118 may be configured for trans-catheter deployment. In some cases, this means that the housing 1118 has overall dimensions that enable the IMD 1102 to fit within a catheter or similar device for delivering the IMD 1102 via a vascular approach. In some cases, the housing 1118 may have an overall length of perhaps about five centimeters or less, or perhaps about three centimeters or less, and/or an overall width of perhaps about 2 centimeters or less, or perhaps about 1 centimeter or less.

In various embodiments, receiving coil 1112 may be disposed within the housing 1118 and receiving coils 1114 and 1116 may be disposed outside the housing 1118. In some cases, receiving coils 1112, 1114, and 1116 may all be within the housing 1118, or the receiving coils 1112, 1114, and 1116 may all be outside of the housing. These are just examples.

In certain embodiments, the receiving coils 1112, 1114, and 1116 may be configured to receive near-field energy. The charging circuitry 1104 may be operably coupled with the receiving coils 1112, 1114, and 1116 and the rechargeable power source 1106. In some cases, the charging circuitry 1104 may be configured to charge the rechargeable power source 1106 using the near-field energy received by the receiving coils 1112, 1114, and 1116. In some cases, the receiving coils 1112, 1114, and 1116 may be configured to receive sufficient near field energy from a wavelength band of near-field energy transmitted from outside the patient 700 (FIG. 6) to recharge the rechargeable power source 1106 at a rate faster than the rechargeable power source 1106 is depleted by powering the IMD 1102 when the wavelength band of near-field energy is transmitted at an intensity that does not cause heat damage to the patient 700. In some cases, the housing 1118 has a substantially cylindrical profile and the receiving coil 1112 may be conformed to the substantially cylindrical profile of an inner surface of an inner cavity defined by the housing 1118.

In some cases, the charging circuitry 1104 and the therapeutic circuitry 1108 may be located on distinct circuit boards or may be manifested within distinct integrated circuits (ICs). In some cases, the charging circuitry 1104 and the therapeutic circuitry 1108, while shown as distinct elements, may be combined within a single IC or on a single circuit board. In some cases, the therapeutic circuitry 1108 may be operatively coupled to the electrodes 1110 a and 1110 b. In some instances, the therapeutic circuitry 1108 may be configured to sense one or more signals via the electrodes 1110 a and 1110 b (or additional electrodes) and/or to stimulate tissue via the electrodes 1110 a and 1110 b. In some cases, the therapeutic circuitry 1108 may pace, or stimulate tissue, at least partly in response to the one or more sensed signals.

FIG. 11 provides a schematic view of another illustrative IMD 1202 that may be configured to be implanted within a patient such as the patient 700 (FIG. 6). In some cases, electrodes 1210 and 1212 may be remote from a housing 1220 of the IMD 1202 and may be operably coupled to therapeutic circuitry 1208. While two electrodes are illustrated, it will be appreciated that in some instances the IMD 1202 may include three, four or more distinct electrodes. Depending on the intended functionality of the IMD 1202, the electrodes 1210 and 1212 may be used for sensing and/or pacing the patient's heart. In some instances, for example, the IMD 1202 may be an LCP, an implantable monitoring device or an implantable sensor. In some cases, the electrodes 1210 and 1212 may be used for communicating with other implanted devices and/or with external devices. In some cases, communication with other implanted devices may include conductive communication, but this is not required.

In some cases, the electrodes 1210 and 1212 may include receiving coils 1214 and 1216, and in some cases another receiving coil 1218 may be disposed within the housing 1220. In certain embodiments, the receiving coils 1214, 1216, and 1218 may be configured to receive near-field energy. The charging circuitry 1204 may be operably coupled with the receiving coils 1214, 1216, and 1218 and the rechargeable power source 1206. In some cases, the charging circuitry 1204 may be configured to charge the rechargeable power source 1206 using the near-field energy received by the receiving coils 1214, 1216, and 1218. In some cases, the receiving coils 1214, 1216, and 1218 may be configured to receive sufficient near-field energy from a wavelength band of near-field energy transmitted from outside the patient 700 (FIG. 6) to recharge the rechargeable power source 1206 at a rate faster than the rechargeable power source 1206 is depleted by powering the IMD 1202 when the wavelength band of near-field energy is transmitted at an intensity that does not cause heat damage to the patient 700. In some cases, the housing 1220 has a substantially cylindrical profile and the receiving coil 1218, if present, may be conformed to the substantially cylindrical profile of an inner surface of an inner cavity defined by the housing 1220, but this is not required. In some cases, the rechargeable power source 1206 may be disposed within the housing 1220 and may be configured to power the IMD 1202, including the therapeutic circuitry 1208.

In some cases, the charging circuitry 1204 and the therapeutic circuitry 1208 may be located on distinct circuit boards or be manifested within distinct integrated circuits (ICs). In some cases, the charging circuitry 1204 and the therapeutic circuitry 1208, while shown as distinct elements, may be combined within a single IC or on a single circuit board. In some cases, the therapeutic circuitry 1208 may be operatively coupled to the electrodes 1210 and 1212. In some instances, the therapeutic circuitry 1208 may be configured to sense one or more signals via the electrodes 1210 and 1212 (or additional electrodes) and/or to stimulate tissue via the electrodes 1210 and 1212. In some cases, the therapeutic circuitry 1208 may pace, or stimulate tissue, at least partly in response to the one or more sensed signals.

According to various embodiments, the housing 1220 may be configured for trans-catheter deployment. In some cases, this means that the housing 1220 has overall dimensions that enable the IMD 1202 to fit within a catheter or similar device for delivering the IMD 1202 via a vascular approach. In some cases, the housing 1220 may have an overall length of perhaps about five centimeters or less, or perhaps about three centimeters or less, and/or an overall width of perhaps about 2 centimeters or less, or perhaps about 1 centimeter or less.

FIG. 12 illustrates an example of another illustrative IMD 1300 (e.g., a leadless cardiac pacemaker (LCP)) implanted in a chamber of a heart H, such as the left ventricle LV. A cross-sectional view of the illustrative implantable medical device 1300 is shown in FIG. 12. The IMD 1300 may include a shell or housing 1302 having a proximal end 1304 and a distal end 1306. The IMD 1300 may include a first electrode 1308 positioned adjacent to the distal end 1306 of the housing 1302 and a second electrode 1310 positioned adjacent to the proximal end 1304 of the housing 1302. The electrodes 1308, 1310 may be sensing and/or pacing electrodes to provide electro-therapy and/or sensing capabilities. The first electrode 1308 may be capable of being positioned against or may otherwise in contact with the cardiac tissue of the heart H while the second electrode 1310 may be spaced away from the first electrode 1308, and in some cases spaced away from the cardiac tissue.

The illustrative IMD 1300 may include a pulse generator (e.g., therapeutic circuitry 1312), and a rechargeable power source 1314 (e.g., a rechargeable battery) within the housing 1302 to provide electrical signals to the electrodes 1308, 1310 and thus control the pacing/sensing electrodes 1308, 1310. Electrical communication between the therapeutic circuitry 1312 and the electrodes 1308, 1310 may provide electrical stimulation to heart tissue and/or sense a physiological condition.

The illustrative IMD 1300 may include a fixation mechanism 1316 proximate the distal end 1306 of the housing 1302 configured to attach the implantable device 1300 to a tissue wall of the heart H, or otherwise anchor the IMD 1300 to the anatomy of the patient. As shown in FIG. 12, in some instances, the fixation mechanism 1316 may include one or more, or a plurality of hooks or tines anchored into the cardiac tissue of the heart H to attach the implantable device 1300 to a tissue wall. In other instances, the fixation mechanism 1316 may include one or more, or a plurality of passive tines, configured to entangle with trabeculae within the chamber of the heart H and/or a helical fixation anchor configured to be screwed into a tissue wall to anchor the IMD 1300 to the heart H.

The illustrative IMD 1300 may include a docking member 1318 proximate the proximal end 1304 of the housing 1302 configured to facilitate delivery and/or retrieval of the IMD 1300. For example, the docking member 1318 may extend from the proximal end 1304 of the housing 1302 along a longitudinal axis of the housing 1302. The docking member 1318 may include a head portion 1320 and a neck portion 1322 extending between the housing 1302 and the head portion 1320. The head portion 1320 may be an enlarged portion relative to the neck portion 1322. For example, the head portion 1320 may have a radial dimension from the longitudinal axis of the IMD 1300 which is greater than a radial dimension of the neck portion 1322 from the longitudinal axis of the IMD 1300. The docking member 1318 may further include a tether retention structure 1324 extending from the head portion 1320. The tether retention structure 1324 may define an opening 1326 configured to receive a tether or other anchoring mechanism therethrough. While the retention structure 1324 is shown as having a generally “U-shaped” configuration, the retention structure 1324 may take any shape which provides an enclosed perimeter surrounding the opening 1326 such that a tether may be securably and releasably passed (e.g. looped) through the opening 1326. The retention structure 1324 may extend though the head portion 1320, along the neck portion 1322, and to or into the proximal end 1304 of the housing 1302. The docking member 1318 may be configured to facilitate delivery of the IMD 1300 to the intracardiac site and/or retrieval of the IMD 1300 from the intracardiac site. Other docking members 1318 are contemplated.

In some cases, the IMD 1300 may include receiving coils 1328, 1330, 1332, and 1334 configured to receive a non-radiative near-field energy through a patient's body. The receiving coils may include fixation mechanisms 1344, 1346, and 1348 similar to the fixation mechanism 1316.

The receiving coils 1328, 1330, 1332, and 1334 are used in an “inductive” charging systems that operates in the non-radiative near-field region. In inductive power systems, power is typically transferred over short distances by magnetic fields (i.e. magnetic field 1340) using inductive coupling between coils of wire, such as source coil 1338 and receiving coils 1328, 1330, 1332, and 1334. In some cases, a source 1336 may apply the magnetic field 1340 that operates at a frequency greater than or equal to 10 kHz and less than or equal to 100 MHz. When so provided, the source 1336 and the IMD 1300 may operate in the non-radiative near-field energy region. In addition, in some instances, a ratio between the frequency of operation of the applied magnetic field and a dimension of the receiving coils 1328, 1330, 1332, and 1334 may affect a generated radiated field. For example, when an outer dimension of receiving coils 1328, 1330, 1332, and 1334 is less than 1/10 of the wavelength of the applied magnetic field, the radiated field may be minimized.

In some cases, as shown in FIG. 12, the receiving coils 1328, 1330, and 1332 may be disposed outside the housing 1302 and tethered relative to the housing 1302 (e.g., using the tether retention structure 1324). Furthermore, the receiving coil 1334, if present, may be disposed within the housing 1302. In some cases, a signal generator circuitry 1341 may generate an AC through the source coil 1338 and create an oscillating magnetic field 1340. The magnetic field 1340 may pass through the receiving coils 1328, 1330, 1332, and 1334 and induce an alternating EMF, which creates an alternating current. The receiving coils 1328, 1330, 1332, and 1334 may be operatively coupled to charging circuitry 1342 and pass the induced AC to the charging circuitry 1342. In certain embodiments, the charging circuitry 1342 may also be operatively coupled with the rechargeable power source 1314. In some cases, the charging circuitry 1342 may be configured to charge the rechargeable power source 1314 using the AC received from the receiving coils 1328, 1330, 1332, and 1334. In some cases, the receiving coils 1328, 1330, 1332, and 1334 may be configured to receive sufficient near-field energy from the magnetic field 1340 transmitted from the source 1336 to recharge the rechargeable power source 1314, at a rate faster than the rechargeable power source 1314 is depleted powering the IMD 1300, when the magnetic field 1340 is transmitted at an intensity that does not cause heat damage to the patient 700. In some cases, the charging circuitry 1342 may use power summing to sum the power from each of the receiving coils 1328, 1330, 1332, and 1334. In some cases, the charging circuitry 1342 may including a switching circuit to selectively select one or more of the receiving coils 1328, 1330, 1332, and 1334 to charge the rechargeable power source 1314.

In some cases, the charging circuitry 1342 may monitor the magnetic field 1340 and detect the power delivered to the rechargeable power source 1314. In some cases, the charging circuitry 1342 may detect that the power delivered has decreased due to the primary capture axis of the receiving coil 1328 no longer aligning with the primary transfer axis of the source coil 1338. The charging circuitry 1342 may also detect that the primary capture axis of the receiving coil 1332 is in closer alignment with the primary transfer axis of the source coil 1338. As a result, the charging circuitry 1342 may select the receiving coil 1332 to inductively couple with the source coil 1338 and the power delivered to the rechargeable power source 1314 will be from the AC created by the alternating EMF in the receiving coil 1332. This is just one example of the use of a switching circuit.

In some cases, one or more of the receiving coils 1328, 1330, 1332, and 1334 may be fitted with a ferrite core (not shown). The permeability, relative to the surrounding environment, may cause the magnetic field 1340 to be concentrated in the ferrite core. In some cases, the use of the ferrite core can concentrate the strength and increase the effect of the magnetic field 1340 produced. The magnetic field 1340 may also be confined and guided, using the ferrite cores, and may improve coupling, thus, improving the transfer of power. In some cases, to increase the benefits of a ferrite core, the diameter of the receiving coils 1328, 1330, 1332, and 1334 may be relatively small compared to their lengths. For example, to benefit from the ferrite cores, a ratio between the length of the receiving coils 1328, 1330, 1332, and 1334 and their diameters may be 3 to 1 or greater. In another example, to benefit from the ferrite cores, the ratio between the length of the receiving coils 1328, 1330, 1332, and 1334 and their diameters may be 10 to 1 or greater. In some cases, the receiving coils 1328, 1330, 1332, and 1334 may be spaced from one another and may each may have a primary capture axis that is not-aligned with the primary capture axis of at least one other receiving coil.

In some cases, the source coil 1338 may be resonantly inductively coupled to one or more of the receiving coils 1328, 1330, 1332, and 1334. For example, the source 1336 may be tuned such that the source coil 1338 resonates at the same frequency as one or more of the receiving coils 1328, 1330, 1332, and 1334, in some cases, the resonance between the source coil 1338 and one or more of the receiving coils 1328, 1330, 1332, and 1334 may increase the power transferred. In some cases, when the source 1336 and the MD 1300 achieve resonant inductive coupling, the source 1336 and the IM D 1300 may interact with each other more strongly than they do with non-resonant objects and power losses due to absorption in stray nearby objects may be reduced or negligible.

FIG. 13 illustrates another example IMD 1400 (e.g., a leadless cardiac pacemaker (LCP)) implanted in a chamber of a heart H, such as the left ventricle LV. The IMD 1400 may include a housing 1402, electrodes 1408 and 1410, receiving coils 1428, 1430, 1432, and 1434, fixation mechanisms 1416, 1444, 1446, and 1448, a docking member 1418, a tether retention structure 1424, therapeutic circuitry 1412, a rechargeable power source 1414, and charging circuitry 1442. The configuration and operation the IMD 1400 and its elements may be similar to the configuration and operation of the IMD 1300 and its elements described with respect to FIG. 12. In some cases, as seen in FIG. 13, the IMD 1400 may also include remote electrodes 1450, 1452, and 1454 disposed outside the housing 1402 of the IMD 1400 and tethered relative to the housing 1402 (e.g., using the tether retention structure 1424). The remote electrodes 1450, 1452, and 1454 may be sensing and/or pacing electrodes to provide electro-therapy and/or sensing capabilities. In some cases, the electrodes 1450, 1452, and 1454 may be capable of being positioned against or may otherwise contact the cardiac tissue of the heart H. The IMD 1400 may also include a pulse generator (e.g., the therapeutic circuitry 1412), and the rechargeable power source 1414 (e.g., a rechargeable battery) within the housing 1402 operatively coupled to the electrodes 1450, 1452, and 1454 to provide electrical signals to the electrodes 1450, 1452, and 1454 and thus control the pacing/sensing electrodes 1450, 1452, and 1454. Electrical communication between the therapeutic circuitry 1412 and the electrodes 1450, 1452, and 1454 may provide electrical stimulation to heart tissue and/or sense a physiological condition.

The remote electrodes 1450, 1452, and 1454 may include fixation mechanisms 1444, 1446, and 1448 proximate a distal end of an electrode housing 1456, 1458, and 1460 configured to attach the remote electrodes 1450, 1452, and 1454 to a tissue wall of the heart H, or otherwise anchor the remote electrodes 1450, 1452, and 1454 to the anatomy of the patient. As shown in FIG. 13, in some instances, the fixation mechanisms 1444 1446, and 1448 may include one or more, or a plurality of hooks or tines anchored into the cardiac tissue of the heart H to attach the remote electrodes 1450, 1452, and 1454 to a tissue wall. In other instances, the fixation mechanisms 1444, 1446, and 1448 may include one or more, or a plurality of passive tines, configured to entangle with trabeculae within the chamber of the heart H and/or a helical fixation anchor configured to be screwed into a tissue wall to anchor the remote electrodes 1450, 1452, and 1454 to the heart H.

In some cases, one or more of the remote electrodes 1450, 1452, and 1454 may also include a receiving coil, such as receiving coils 1428, 1430, and 1432. As previously stated, the receiving coils 1428, 1430, and 1432 may be configured to operate similar to the receiving coils 1328, 1330, 1332, as described with respect to FIG. 12.

FIG. 14 illustrates another example an IMD 1500 (e.g., a leadless cardiac pacemaker (LCP)) implanted in a chamber of a heart H, such as the left ventricle LV. The IMD 1500 may include a housing 1502, electrodes 1508 and 1510, receiving coils 1528, 1530, and 1532, fixation mechanism 1516, a docking member 1518, a tether retention structure 1524, therapeutic circuitry 1512, a rechargeable power source 1514, and charging circuitry 1542. The configuration and operation the IMD 1500 and its elements may be similar to the configuration and operation of the IMD 1300 and its elements described with respect to FIG. 12. In some cases, as seen in FIG. 14, the IMD 1500 may include the receiving coils 1528, 1530, and 1532 disposed outside the housing 1502, and may be configured to move from a pre-deployment, compressed state, to an expanded post-deployment state. For example, the receiving coils 1528, 1530, and 1532 may be attached to a distal end of the housing 1502 of the IMD in any suitable manner, which may include hinges, screws, pins and/or any other suitable fastener so that joints 1560, 1562, and 1564 are formed at a distal end of the receiving coils 1528, 1530, and 1532. In some cases, the joints 1560, 1562, and 1564 may be configured to pivot so that a proximal end of the receiving coils 1528, 1530, and 1532 move, retract, or compress towards the housing 1502 to a closed position. In some cases, the joints 1560, 1562, and 1564 may be further configured to pivot so that the proximal end of the receiving coils 1528, 1530, and 1532 move, expand, or swing away from the housing 1502 to an open position.

For another example, the receiving coils 1528, 1530, and 1532 may be attached to a proximal end of the housing 1502 of the IMD in any suitable manner, which may include hinges, screws, pins and/or any other suitable fastener so that joints 1560, 1562, and 1564 are formed at a proximal end of the receiving coils 1528, 1530, and 1532. In some cases, the joints 1560, 1562, and 1564 may be configured to pivot so that a distal end of the receiving coils 1528, 1530, and 1532 move, retract, or compress towards the housing 1502 to a closed position. In some cases, the joints 1560, 1562, and 1564 may be further configured to pivot so that the distal end of the receiving coils 1528, 1530, and 1532 move, expand, or swing away from the housing 1502 to an open position.

In the open position, the receiving coils 1528, 1530, and 1532 may each have a primary capture axis along which a maximum amount of non-radiative near-field energy is captured. As discussed herein, a transfer of power may increase when a primary transfer axis of a source coil (i.e., source coil 1538) of a source (i.e., source 1536) is at least partially aligned with a primary capture axis of one or more of the receiving coils 1528, 1530, and 1532. Furthermore, the primary transfer axis of the source coil 1538 may change during a given time. Therefore, in some cases, the IMD 1500 may be configured such that the primary capture axis of one or more of the receiving coils 1528, 1530, and 1532 may be non-parallel with the primary capture axis of another one of the receiving coils 1528, 1530, and 1532. In this configuration, the IMD 1500 may have a greater chance of one of the primary receiving axis of the receiving coils 1528, 1530, and 1532 being at least partially aligned with the primary transfer axis of the source coil 1538 so as to increase the power transfer efficiency. In some cases, two or more of the receiving coils 1528, 1530, and 1532 may be at least partially aligned with the primary transfer axis of the source coil 1538. In some cases, the receiving coils 1528, 1530, and 1532 are orientated to be orthogonal or substantially orthogonal to each other.

In some cases, the receiving coils 1528, 1530, and 1532 may be in the closed state before and during deployment of the IMD 1500, and in the open state after deployment of the IMD 1500. For example, the IMD 1500 may initially be located in a holding section of a delivery catheter. In the holding section, the receiving coils 1528, 1530, and 1532 may be compressed or retracted by an inner-wall of the holding section of the delivery catheter. Once the holding section has been positioned adjacent to cardiac tissue at a desired implantation site, the IMD 1500 may be distally advanced out of the holding section of the delivery catheter. During this process, the fixation mechanism 1516 may engage the heart tissue, and the delivery catheter, including the holding section, can be proximally retracted. Once, the holding section has been retracted, the inner-wall may no longer compress or retract the receiving coils 1528, 1530, and 1532, allowing the receiving coils 1528, 1530, and 1532 to open. In some cases, the receiving coils 1528, 1530, and 1532 may include a shape memory alloy such as Nitinol that is biases the receiving coils 1528, 1530, and 1532 toward the open position.

As discussed herein, in some cases, the source 1536 may apply a magnetic field 1540 that operates at a frequency greater than or equal to 10 kHz and less than or equal to 100 MHz. When so provided, the source 1536 and the IMD 1500 may operate in the non-radiative near-field energy region. In addition, in some instances, a ratio between the frequency of operation of the applied magnetic field and a maximum dimension of the receiving coils 1528, 1530, and 1532, may affect a generated radiated field. For example, when a maximum outer dimension of receiving coils 1528, 1530, and 1532, is less than 1/10 of the wavelength of the applied magnetic field, the radiated field may be minimized, which in this instance may be desirable.

Also discussed herein, in some cases, the receiving coils 1528, 1530, and 1532 may be in a power summation configuration. As discussed with respect to FIG. 8, a power summation configuration may be used to increase the overall power transferred from the source 1536 to the IMD 1500. For example, the source 1536 may transmit the near-field energy such that the receiving coils 1528, 1530, and 1532 may simultaneously or sequentially capture the near-field energy and transfer it to the charging circuitry 1542. In some cases, the magnetic field 1540 may pass through at least two of the receiving coils 1528, 1530, and 1532. The alternating current (AC) created from the alternating EMF from the induced receiving coils may combine using a non-linear circuit element (e.g. diodes) and increase the total power delivered to the rechargeable power source 1514. In this configuration, the 1500 may increase the power transfer efficiencies to help overcome the receiving coils 1528, 1530, and 1532 spatial geometries (e.g., misalignment of their primary capture axes with the transfer axis of the source coil 1538), the distance between the source coil 1538 and the receiving coils 1528, 1530, and 1532, changes in resonant frequency and/or other factors.

The receiving coils 1528, 1530, and 1532 may be any of a variety of different types of receiving coils. Although flat (winged) coils are shown, the receiving coils 1528, 1530, and 1532 may take on many other shapes and configurations. Moreover, although three coils are shown, it will be appreciated that in some instances, the IMD 1500 may include one, two, four or more distinct receiving coils. In some cases, the receiving coils 1528, 1530, and 1532 may be made of shaped-formed materials such as nitinol. In some cases, the receiving coils 1528, 1530, and 1532 may be conformal to the myocardium of the heart when in the open position. In some cases, the receiving coils 1528, 1530, and 1532 may be stiff. In some cases, the receiving coils 1528, 1530, and 1532 may contain both endothialization-promoting and anti-thrombotic coatings (e.g., Dacron sock, PEG, etc.). In some cases, the receiving coils 1528, 1530, and 1532 may have localized strain-relief added that may reduce wear-out (e.g., use of meandering interconnect at the joints). In some cases, the receiving coils 1528, 1530, and 1532 may contain ferrite materials that may improve the local magnetic flux. In some cases, a substrate of the receiving coils 1528, 1530, and 1532 may incorporate ferrous material such that the local flux density may be increased. In some cases, the receiving coils 1528, 1530, and 1532 may be a part of the housing 1502 and open up after deployment. In some cases, the receiving coils 1528, 1530, and 1532 may be used for inductive communication. In some cases, the receiving coils 1528, 1530, and 1532 may be used for acoustic energy transfer. In some cases, the receiving coils 1528, 1530, and 1532 may have their own resonance capacitor and rectifier to provide localized rectification. In some cases, the receiving coils 1528, 1530, and 1532 could be a single-coil compound that covers three distinct planes. In some cases, the receiving coils 1528, 1530, and 1532 may be used for capacitive recharge. In some cases, the receiving coils 1528, 1530, and 1532 may be rod shaped and serially co-aligned during catheter delivery to reduce the diametric space taken up in the holding section of the delivery catheter.

FIG. 15 illustrates another example an IMD 1600 (e.g., an implantable cardiac pacemaker) implanted in a chamber of a heart H, such as the left ventricle LV. Although configured differently, the IMD 1600 and its elements may operate similar to IMD 1300 and its elements. For instance, in some cases, the IMD 1600 may include electrodes 1602, 1604, 1606, and 1608 operably coupled to therapeutic circuitry 1622. While four electrodes are illustrated, it will be appreciated that in some instances the IMD 1600 may include one, two, three, five or more distinct electrodes and/or sensors. Depending on the intended functionality of the IMD 1600, the electrodes 1602, 1604, 1606, and 1608 may be used for sensing and/or pacing the patient's heart. In some instances, for example, the IMD 1600 may be a monitoring device or an implantable sensor. In some cases, the electrodes 1602, 1604, 1606, and 1608 may be used for communicating with other implanted devices and/or with external devices. In some cases, communication with other implanted devices may include conductive communication, but this is not required. The IMD 1600 may also include a rechargeable power source 1612 and may be configured to power the IMD 1600, including therapeutic circuitry 1622.

According to various embodiments, the IMD 1600 may be configured for trans-catheter deployment. In some cases, this means that the IMD 1600 has pre-deployment dimensions that enable the IMD 1600 to fit within a delivery catheter or similar device for delivering the IMD 1600 via a vascular approach.

In various embodiments, the IMD 1600 may also include receiving coils 1614, 1616, 1618, and 1620. In certain embodiments, the receiving coils 1614, 1616, 1618, and 1620 may be configured to receive near-field energy. The charging circuitry 1610 may be operably coupled with the receiving coils 1614, 1616, 1618, and 1620 and the rechargeable power source 1612. In some cases, the charging circuitry 1610 may be configured to charge the rechargeable power source 1612 using the near-field energy received by the receiving coils 1614, 1616, 1618, and 1620. In some cases, the receiving coils 1614, 1616, 1618, and 1620 may be configured to receive sufficient near-field energy from a wavelength band of near-field energy transmitted from outside the patient 700 (FIG. 6) to recharge the rechargeable power source 1612 at a rate faster than the rechargeable power source 1612 is depleted by powering the IMD 1600 when the wavelength band of near-field energy is transmitted at an intensity that does not cause heat damage to the patient 700.

In some cases, the charging circuitry 1610 and the therapeutic circuitry 1622 may be located on distinct circuit boards or be manifested within distinct integrated circuits (ICs). In some cases, the charging circuitry 1610 and the therapeutic circuitry 1622, while shown as distinct elements, may be combined within a single IC or on a single circuit board. In some cases, the therapeutic circuitry 1622 may be operatively coupled to the electrodes 1602, 1604, 1606, and 1608. In some instances, the therapeutic circuitry 1622 may be configured to sense one or more signals via the electrodes 1602, 1604, 1606, and 1608 (or additional electrodes) and/or to stimulate tissue via the electrodes 1602, 1604, 1606, and 1608. In some cases, the therapeutic circuitry 1622 may pace, or stimulate tissue, at least partly in response to the one or more sensed signals.

In some cases, the receiving coils 1614, 1616, 1618, and 1620 may be in a power summation configuration. As discussed with respect to FIG. 8, a power summation configuration may be used to increase the overall power transferred from a source 1636 to the IMD 1600. For example, the source 1636 may transmit the near-field energy such that the receiving coils 1614, 1616, 1618, and 1620 may simultaneously or sequentially capture the near-field energy and transfer it to the charging circuitry 1610. In some cases, the magnetic field 1640 may pass through at least two of the receiving coils 1614, 1616, 1618, and 1620. The alternating current (AC) created from the alternating EMF from the induced receiving coils may combine using a non-linear circuit element (e.g. diodes) and increase the total power delivered to the rechargeable power source 1612. In this configuration, the IMD 1600 may increase the power transfer efficiencies to help overcome the receiving coils 1614, 1616, 1618, and 1620 spatial geometries (e.g., misalignment of their primary capture axes with the transfer axis of a source coil 1638), the distance between the source coil 1638 and the receiving coils 1614, 1616, 1618, and 1620, changes in resonant frequency and/or other factors.

In some cases, the receiving coils 1614, 1616, 1618, and 1620 may be fitted with a ferrite core (not shown). The permeability, relative to the surrounding environment, may cause a magnetic field 1640 to be concentrated in the ferrite core. In some cases, the use of the ferrite core can concentrate the strength and increase the effect of the magnetic field 1640 produced. The magnetic field 1640 may also be confined and guided, using the ferrite cores, and may improve coupling, thus, improving the transfer of power. In some cases, to increase the benefits of a ferrite core, the diameter of the receiving coils 1614, 1616, 1618, and 1620 should be relatively small compared to their lengths. For example, to benefit from the ferrite cores, a ratio between the length of the receiving coils 1614, 1616, 1618, and 1620 and their diameters may be greater than or equal to 2 to 1. In another example, to benefit from the ferrite cores, the ratio between the length of the receiving coils 1614, 1616, 1618, and 1620 and their diameters may be greater than or equal to 10 to 1.

In some cases, the IMD 1600 may include a flexible substrate 1650. In certain embodiments, the flexible substrate 1650 may be configured to expand from a delivery state to a deployed state and conform to an inner surface of the heart H. In some cases, the flexible substrate 1650 may comprise a flex circuit with the receiving coils 1614, 1616, 1618, and 1620, the therapeutic circuitry 1622, the charging circuitry 1610, and the rechargeable power source 1612. In some cases, the flexible substrate 1650 may have one or more tines, barbs or other fixation elements that help fix the flexible substrate 1650 in place on the inner surface of the heart H.

FIG. 16A is a view of an illustrative delivery device 1700 (e.g., a catheter) that may be used to deliver an IMD 1702 (e.g., a leadless cardiac pacemaker (LCP)) in a chamber of a heart H, such as the left ventricle LV or right ventricle RV. The delivery device 1700 may include a distal holding section 1712 that may define a cavity 1714 for slidably receiving the IMD 1702, and may include a distal opening 1716 for slidable insertion and/or extraction of the IMD 1702 into and/or out of the cavity 1714. In some cases, receiving coils 1706, 1708, and 1710 may be disposed outside a housing 1704 of the IMD 1702 and tethered relative to the housing 1704 (e.g., using a tether retention structure 1724).

In some cases, a distal end 1718 of the distal holding section 1712 may be placed next to and in contact with a wall 1720 of the chamber of heart H and deployment of the IMD 1702 can begin. FIG. 16B is a view of an implantable IMD 1702 in the delivery device 1700. As the IMD 1702 is pushed distally, fixation mechanisms 1722 may engage the heart tissue of the heart chamber wall 1720. The IMD 1702 may be distally advanced out of the distal holding section 1712 to deploy the fixation mechanisms 1722 from the distal holding section 1712 and engage the fixation mechanisms 1722 in the heart tissue.

Once the fixation mechanisms 1722 have sufficiently engaged the heart wall 1720, as shown in FIG. 16C, the remainder of the IMD 1702 (e.g., the receiving coils 1706, 1708, and 1710) may be expelled from the distal holding section 1712 and the delivery device 1700 may be retracted. In some cases, the inductive coupling between a source coil (not shown) and the receiving coils 1706, 1708, and 1710 may depend on their geometry (e.g. orientation, size, shape, etc.) and the distance between them. For example, when the source coil is aligned with one or more of the receiving coils 1706, 1708, and 1710 such that a magnetic field (not shown) flows directly or nearly directly through one or more of the receiving coils 1706, 1708, and 1710, the power transfer efficiency may increase. In addition, the power transfer efficiency may increase when one or more of the receiving coils 1706, 1708, and 1710 are close enough to the source coil such that the magnetic field reaches one or more of the receiving coils 1706, 1708, and 1710 before the magnetic field has diverged substantially.

In some cases, the receiving coils 1706, 1708, and 1710 may include fixation mechanisms 1726, 1728, and 1730 configured to engage the heart tissue of the chamber wall 1720 and secure each of the receiving coils 1706, 1708, and 1710 to a corresponding location along the chamber wall 1720. As shown in FIG. 16D, as the delivery device is retracted, the receiving coils 1706, 1708, and 1710 may each be guided and fixed to implantation locations that are spaced from one another such that the receiving coils 1706, 1708, and 1710 have primary capture axes that are not parallel, and in some case, orthogonal. When so provided, the IMD 1702 may have a greater chance that a primary capture axis of the receiving coils 1706, 1708, and 1710 substantially aligns with the primary transfer axis of the source coil such that the magnetic field flows directly or nearly directly through one or more of the receiving coils 1706, 1708, and 1710.

FIG. 17A is a view of an illustrative delivery device 1800 (e.g., a catheter) that may be used to deliver an IMD 1802 (e.g., a leadless cardiac pacemaker (LCP)) in a chamber of a heart H, such as the left ventricle LV or the right ventricle RV. The delivery device 1800 may include a distal holding section 1812 that may define a cavity 1814 for slidably receiving the IMD 1802, and may include a distal opening 1816 for slidable insertion and/or extraction of the IMD 1802 into and/or out of the cavity 1814. In some cases, the IMD 1802 may include the receiving coils 1806, 1808, and 1810 disposed outside a housing 1804 and configured to move from a pre-deployment, compressed state, to an expanded post-deployment state. For example, the receiving coils 1806, 1808, and 1810 may be attached to a distal end (or proximal end) of the housing 1804 by any suitable mechanism such as hinges, screws, pins and./or any other suitable fastener or joint so that joints 1830, 1832, and 1834 are formed at a distal end (or proximal end) of the receiving coils 1806, 1808, and 1810. In some cases, the joints 1830, 1832, and 1834 may be configured to pivot so that a proximal end (or distal end) of the receiving coils 1806, 1808, and 1810 move, retract, or compress towards the housing 1804 to a closed position. In some cases, the joints 1830, 1832, and 1834 may be further configured to pivot so that the proximal end (or distal end) of the receiving coils 1806, 1808, and 1810 move, expand, or swing away from the housing 1804 to an open position. These are just some examples.

In some cases, a distal end 1818 of the distal holding section 1812 may be placed next to and in contact with a wall 1820 of the chamber of heart H and deployment of the IMD 1802 can begin. FIG. 17B is a view of an implanted IMD 1802 by the delivery device 1800. As the IMD 1802 is pushed distally, fixation mechanisms 1822 engage the heart tissue of the chamber wall 1820. The IMD 1802 may be distally advanced out of the distal holding section 1812 to deploy the fixation mechanisms 1822 from the distal holding section 1812 and engage the fixation mechanisms 1822 in the heart tissue.

Once the fixation mechanisms 1822 have sufficiently engaged the heart wall 1820, as shown in FIG. 17C, the remainder of the IMD 1802 may be expelled from the distal holding section 1812 and the delivery device 1800 may be retracted. In some cases, the receiving coils 1806, 1808, and 1810 may be compressed or retracted by an inner-wall 1824 of the distal holding section 1812. Once the distal holding section 1812 has been retracted, the inner-wall 1824 may no longer compress or retract the receiving coils 1806, 1808, and 1810, allowing the receiving coils 1806, 1808, and 1810 to open, sometimes in an umbrella-like manner.

As shown in FIG. 17D, in the open position, the receiving coils 1806, 1808, and 1810 may each have a primary capture axis along which a maximum amount of non-radiative near-field energy is captured. As discussed herein, a transfer of power may increase when a primary transfer axis of a source coil (not shown) is aligned with a primary capture axis of one or more of the receiving coils 1806, 1808, and 1810. Furthermore, the primary transfer axis of the source coil may change during a given time relative to the primal)) axis of the receiving coils 1806, 1808, and 1810. Therefore, in some cases, the IMD 1802 may be configured such that the primary capture axis of one or more of the receiving coils 1806, 1808, and 1810 may be non-parallel with the primary capture axis of another one of the receiving coils 1806, 1808, and 1810, and in some cases orthogonal. In this configuration, the IMD 1802 may have a greater chance of a primary receiving axis of the receiving coils 1806, 1808, and 1810 substantially aligning with the primary transfer axis of the source coil and may increase the power transfer efficiency.

It should be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of steps without exceeding the scope of the disclosure. This may include, to the extent that it is appropriate, the use of any of the features of one example embodiment being used in other embodiments. 

What is claimed is:
 1. An implantable medical device (IMD) configured to be implanted within a patient, the IMD comprising: a housing configured for trans-catheter deployment; a plurality of electrodes exposed external to the housing; therapeutic circuitry disposed within the housing, the therapeutic circuitry operatively coupled to the plurality of electrodes and configured to sense one or more signals via one or more of the plurality of electrodes and/or to stimulate tissue via one or more of the plurality of electrodes; a rechargeable power source disposed within the housing and configured to power the therapeutic circuitry; a plurality of receiving coils configured to receive non-radiative near-field energy through the patient's body, wherein each of the plurality of receiving coils has a primary capture axis along which a maximum amount of non-radiative near-field energy is captured, and wherein at least one of the plurality of receiving coils has a primary capture axis that is non-parallel with the primary capture axis of another one of the plurality of receiving coils; and charging circuitry operatively coupled with the plurality of receiving coils and the rechargeable power source, the charging circuitry configured to use the non-radiative near-field energy received via the plurality of receiving coils to charge the rechargeable power source.
 2. The IMD of claim 1, wherein at least two of the plurality of receiving coils are operatively coupled in a power summation configuration.
 3. The IMD of claim 1, wherein at least one of the plurality of receiving coils is disposed outside the housing.
 4. The IMD of claim 1, wherein at least one of the plurality of receiving coils is disposed within the housing.
 5. The IMD of claim 4, wherein a ratio of a length of the at least one of the plurality of receiving coils to a diameter of the at least one of the plurality of receiving coils is greater than or equal to 3 to 1, and wherein the at least one of the plurality of receiving coils has a ferrite core.
 6. The IMD of claim 1, wherein the charging circuitry is further configured to: select one of the plurality of receiving coils and to receive non-radiative near-field energy using the selected receiving coil; monitor the non-radiative near-field energy received via the selected receiving coil and detect a predetermined condition; and in response to detecting the predetermined condition, select a different one of the plurality of receiving coils and receive non-radiative near-field energy using the different one of the plurality of receiving coils.
 7. The IMD of claim 1, wherein at least one of the plurality of receiving coils are non-planar and form a three-dimensional surface.
 8. The IMD of claim 1, wherein a maximum outer dimension of at least one of the plurality of receiving coils is less than 1/10 of the wavelength of an applied magnetic field supplying the non-radiative near-field energy and the applied magnetic field has a frequency that is greater than or equal to 10 kHz and less than or equal to 100 MHz.
 9. The IMD of claim 1, wherein the plurality of receiving coils are further configured to establish an inductive communication link with an external device.
 10. The IMD of claim 1, wherein the IMD is a leadless cardiac pacemaker (LCP).
 11. The IMD of claim 1, wherein one of the plurality of electrodes is carried by a first remote electrode unit that is remote from but tethered relative to the housing and includes a fixation structure for fixing the first remote electrode unit at a first location in the patient, and wherein the first remote electrode unit carries one of the plurality of receiving coils; and wherein another one of the plurality of electrodes is carried by a second remote electrode unit that is remote from but tethered relative to the housing and includes a fixation structure for fixing the second remote electrode unit at a second location in the patient, and wherein the second remote electrode unit carries another one of the plurality of receiving coils.
 12. An implantable medical device (IMD) configured to be implanted within a patient's body, the IMD comprising: one or more sensors; circuitry operatively coupled to the one or more sensors; a rechargeable power source for powering the circuitry; a plurality of receiving coils configured to receive non-radiative near-field energy through the patient's body, the plurality of receiving coils operatively coupled in a power summing configuration, wherein each of the plurality of receiving coils has a primary capture axis along which a maximum amount of non-radiative near-field energy is captured, and wherein at least one of the plurality of receiving coils has a primary capture axis that is non-parallel with the primary capture axis of another one of the plurality of receiving coils; and charging circuitry operatively coupled with the plurality of receiving coils and the rechargeable power source, the charging circuitry configured to use the non-radiative near-field energy received via the plurality of receiving coils to charge the rechargeable power source.
 13. The IMD of claim 12, wherein at least one of the plurality of receiving coils has a ferrite core.
 14. The IMD of claim 13, wherein a ratio of a length of at least one of the plurality of receiving coils to a diameter of the at least one of the plurality of receiving coils is greater than or equal to 2 to
 1. 15. The IMD of claim 12, the IMD further comprises a flexible substrate that is configured to conform to a surface of the patient's heart, and wherein the one or more sensors, the circuitry, the rechargeable power source, the plurality of receiving coils and the charging circuitry are all mounted to the flexible substrate.
 16. The IMD of claim 12, the IMD further comprises a flexible substrate that is configured to conform to a surface of a patient, and wherein at least two of the plurality of receiving coils are fixed to the flexible substrate.
 17. An implantable medical device (IMD) configured to be implanted within a patient's body, the IMD comprising: a housing configured for trans-catheter deployment; a plurality of electrodes exposed external to the housing; therapeutic circuitry disposed within the housing, the therapeutic circuitry operatively coupled to the plurality of electrodes and configured to sense one or more signals via one or more of the plurality of electrodes and/or to stimulate tissue via one or more of the plurality of electrodes; a rechargeable power source disposed within the housing and configured to power the therapeutic circuitry; a plurality of receiving coils disposed outside the housing, operatively coupled to the rechargeable power source, and configured to: receive non-radiative near-field energy through the patient's body, and move from a pre-deployment compressed state to an expanded post-deployment state, wherein in the post-deployment state of each of the plurality of receiving coils has a primary capture axis along which a maximum amount of non-radiative near-field energy is captured, and wherein at least one of the plurality of receiving coils has a primary capture axis that is non-parallel with the primary capture axis of another one of the plurality of receiving coils; and charging circuitry operatively coupled with the plurality of receiving coils and the rechargeable power source, the charging circuitry configured to use the non-radiative near-field energy received via the plurality of receiving coils to charge the rechargeable power source.
 18. The IMD of claim 17, wherein at least two of the plurality of receiving coils are operatively coupled in a power summation configuration.
 19. The IMD of claim 17, wherein a maximum outer dimension of at least one of the plurality of receiving coils is less than 1/10 of the wavelength of an applied magnetic field supplying the non-radiative near-field energy, and wherein the applied magnetic field supplying the non-radiative near-field energy has a frequency that is greater than or equal to 10 kHz and less than or equal to 100 MHz.
 20. The IMD of claim 17, wherein the IMD is a leadless cardiac pacemaker (LCP). 